If you used App Passwords to authorize applications to access your Google Account, you may see errors when you turn off the 2-Step verification. In this case, you need to disable the App verification at first.

2. You’ll see a list of the apps you’ve created App Passwords for. Click Revoke next to the application you no longer want to have access to your account.If you're an Android 4.0+ user, we recommend removing "Android" from the "Connected Sites, Apps, and Services" section.